1. Field of the Invention
The present invention relates to a device which can be applied to a lifting and/or transporting unit for controllably supporting and handling loads by generating a vacuum in one or more suction pads.
2. Description of the Prior Art
The operation of lifting and supporting a load by means of suction pads in contact with a surface of the loads and in which a vacuum is generated is a well known and used technique, especially, for transport purposes inside working areas and therebetween. Known devices of this kind are very simple and usually include, in addition to the suction pad(s) and a vacuum source, means for controlling the connection of the suction pads to the vacuum source or to atmosphere only.
However these known devices have various drawbacks, both during the load gripping step for lifting and transporting the load and during the latter operation. In fact, these known devices do not possess a control to ensure that a sufficient vacuum level has been reached within the suction pads at the time the operator leaves the load to the lifting and transporting unit to which the supporting device is applied. This leads to human errors and requires a certain skill by the operator who must operate the lifting and transporting unit only once a sufficient vacuum level has been reached within the suction pads, but without an excessive time delay for obvious productivity reasons.
However, the greatest drawback of the known supporting devices with suction pads is that they do not include a safety system against an uncontrollable rapid decrease of the absolute vacuum level within the suction pads during the load lifting and/or transporting operation. Such vacuum decrease can occur for various reason, particularly in case of failures of the vacuum generation and transmission system or else because of unforeseen porosity of the surface on which the suction pads are to be placed, or due to maneuvering errors by the operator who erroneously can depress the load release button while the load is still lifted or suspended.
Finally, another drawback of the known devices of this kind is that they have a fixed number of suction pads and/or a fixed arrangement thereof on the lifting tool, so that loads having different features cannot be accommodated by a single device. There are, for example, loads having a small thickness and a large surface which are to be transported edgewise and therefore require that the suction pads be applied to their side surfaces, or loads having uneven surfaces requiring the application of the suction pads at different levels, and so on. Therefore, these differences in the load features require the use of a different device which, of course, results in a lifting device inventory of remarkable costs.